1. Field of the Invention
The prevent invention relates to a system for determining the movement of a track vehicle and, particularly, programmed or remotely controlled movement.
2. Description of the Art
Rotatable, endless tracks are widely used for movably supporting military, industrial and robot vehicles, such as those used in the nuclear industry, for example. Good traction, as well as a reliable, robust design are characteristic of such vehicles. However, a disadvantage occurs for such vehicles when moved without human intervention and, particularly, for robots intended to travel a predefined path.
More specifically, turning a self-propelled, two-track vehicle is controlled as a function of different rotational speeds and, possibly, directions of driving wheels for the respective tracks. There is variable traction between tracks and the ground, however, so that it is impossible to determine from such control even the pivoting center of the vehicle. The resulting loss of precision regarding the position of the vehicle is unacceptable.
Moreover, even in the case of a rectilinear displacement, the tracks can skid if the ground traction becomes inadequate and the transmission of the movement thereof produced by the engine is no longer ensured. Even in the case of a sufficiently adhesive ground surface, it is not possible to prevent some skidding caused in regulating the speed of the tracks.
The movement of the driving wheels and tracks cannot, therefore, characterize the path of such a vehicle along the ground. Account must be taken of this when choosing sensors for control devices for fixing the position and speed of the vehicle.
The maneuverability of the vehicle and, in particular, its ability to pivot when cornering can be improved by slightly raising the front and rear parts of the tracks, as described in French Pat. No. FR-A-2 302 901. The part of each track which is closest to the ground is also kept curved with the aid of a Teflon (polytetrafluoroethylene) bar, which rubs on the inner surface of the track to provide convexity to the latter, oriented downwards. Over at least part of the length of the track, the action of the bar can be completed by castors. However, this design does not make it possible to obtain accurate information on the pivoting axis of the vehicle and is accompanied by a loss of traction on the ground, which can only be accepted because the vehicle is provided with supplementary tracks, which can be raised when cornering.